1. Field of the Invention
The subject invention generally pertains to dock leveler system and more specifically to a bumper that moves in response to movement of a dock leveler deck.
2. Description of Related Art
Dock levelers are often used to compensate for a height difference that may exist between a loading dock platform and the bed of a truck parked at the dock. A dock leveler system typically includes a ramp or deck that is hinged at its back edge to raise or lower its distal front edge to generally match the height of the truck bed. Often an extension plate or lip is pivotally coupled to the ramp to bridge the gap between the ramp""s front edge and a back edge of the truck bed. The ramp and extended lip provide a path for forklift trucks to travel from the loading dock platform and onto the truck bed, thus facilitating loading or unloading the truck.
When a truck backs into the dock, bumpers mounted adjacent the dock leveler are often used to help prevent the rear of the trailer bed from damaging itself or the dock. There are usually two spaced-apart bumpers mounted to the front face of the dock with one on either side of the dock leveler. This allows the lip and pivoting deck to operate within the span between the two bumpers. To prevent a truck from backing up between the two bumpers and striking the dock leveler, the bumpers are usually spaced apart at something less than the full width of a standard size truck. Thus, for dock levelers that operate between such bumpers, the widths of the deck and lip need to be significantly less than that of a standard truck. Unfortunately, in below-dock operation, a relatively narrow deck may limit a forklift""s access to the right and left rear portion of the truck bed, as explained in U.S. Pat. No. 6,070,283.
However, providing an extra wide deck that extends the full width of a standard-width truck may place the bumpers too far apart to effectively engage trucks that are relatively narrow or are off-center to the bumpers. If the bumpers are installed below the front edge of a full-width deck, the bumpers may prevent the deck from descending below the dock platform for xe2x80x9cbelow-dockxe2x80x9d operation. Operating below-dock is a common practice when servicing trucks whose bed is lower than the dock platform.
To avoid a bumper/deck interference problem with below-dock operation, moveable bumpers can be used, such as those disclosed in U.S. Pat. No. 4,420,849 and European Patent 0 040 388. Both references show bumpers that can retract by swinging underneath the deck from their operative position to a stored position. However, the movement of the bumpers is provided by what appears to be hydraulic cylinders. Such cylinders, when dedicated to operating just the bumpers, add substantial cost to a dock leveler system. The cost includes the initial cost plus ongoing maintenance of the cylinders, as well as their related valves, hydraulic lines and controls.
U.S. Pat. No. 5,881,414 shows another example of a bumper whose movement is provided by a dedicated powered cylinder. However, the deck (item 11) is less than the full width of the dock leveler pit, as deck 11 is situated between the independent bumper support beams (item 20). Also, a height differential between deck 11 and beams 20 can create a step along either side edge of deck 11, as shown in the patent""s FIG. 4. Such a step could be a tipping hazard for a forklift and may pose other operational difficulties.
To provide full access to the right and left rear portions of a truck bed, a dock leveler system includes a deck with a moveable bumper that lies within the width of the deck. The bumper is able to move out of the way to avoid interfering with the operation of the deck and to avoid creating an obstacle to a forklift or the like traveling on the deck. The deck engages the bumper, so that the movement of the deck is what moves the bumper, thereby eliminating the need for a separately powered bumper actuator.
In some embodiments, a pivotal deck moves the bumper in one direction, while a spring urges the bumper in an opposite direction.
In some embodiments, the bumper moves linearly.
In some embodiments, the bumper pivots.
In some embodiments, the bumper moves from an operative position facing the rear of a truck parked at the dock to a retracted position underneath the deck.
In some embodiments, the bumper and deck are coupled to each other by way of a mechanism that has an active mode and a disabled mode, such that downward movement of the deck forces the bumper down when in the active mode; however, in the disabled mode the bumper remains substantially stationary as the deck descends to a cross-traffic position.